This invention relates to vehicle wheels, and more particularly to a structure and method for strengthening a vehicle wheel. The invention is particularly useful in an environment in which the vehicle wheel is subjected to high stresses, such as experienced by racing wheels.
In a racing environment, such as high performance stock car racing, the wheels of the car experience high stresses and strains during operation due to high speeds attained by the vehicle. In organized racing, the sanctioning organization sets minimum acceptable standards for certain wheel strength criteria, which must be met by the wheel manufacturer in order for that manufacturer's wheels to be used in a sanctioned race. One test to which such wheels are subjected is a fatigue test, in which a representative wheel is subjected to fatigue stresses simulating those experienced by a wheel during a race. In this type of test, a predetermined moment is applied to the web of the wheel at the location where the wheel would be mounted to the axle of the vehicle, and the wheel is then rotated to simulate race conditions. Alternatively, a testing procedure can be employed such as that disclosed in my co-pending application Ser. No. 07/443,217 filed Nov. 29, 1989 in which the wheel is maintained stationary and the moment is applied through a shaft to which the wheel is mounted, with the load revolving around the shaft. In either case, the number of revolutions before failure of the wheel is measured, and this must meet or exceed standards set by the racing organization in order for that manufacturer's wheel to be acceptable in a sanctioned race.
It is an object of the present invention to provide a wheel structure which provides improved fatigue strength over conventional wheel structures, and a method of making a wheel to provide such improved fatigue strength. It is another object of the invention to provide a wheel for use in a racing environment which is capable of increased endurance under conditions in which severe fatigue stresses are imparted to the wheel, yet which does not detract from the performance of the wheel.
A wheel typically comprises a rim including an inner surface and an outer surface adapted to mount a tire thereto, and mounting structure connected to the inner surface of the rim for mounting the wheel to a vehicle. In accordance with the invention, an area of increased thickness is associated with the rim and extends in a direction circumferentially around the rim, the area of increased thickness is located adjacent the connection of the mounting structure to the rim, and increases the ability of the wheel to withstand fatigue stresses. In one embodiment, the mounting structure comprises a plurality of spaced tabs including openings adapted to receive studs located on a mounting hub, with the tabs being connected to the inner surface of the rim. The area of increased thickness provided to the rim is located adjacent each tab. In a particularly preferred embodiment, the area of increased thickness extends substantially continuously about the circumference of the rim. With a tab-type mounting structure, each tab is connected to the inner surface of the rim adjacent the area of increased thickness. Preferably, the area of increased thickness is located behind the mounting structure, such as the mounting tabs, as viewed when the wheel is mounted to a vehicle.
The area of increased thickness provided to the rim preferably comprises a deformation such as a crimp formed in the rim to create a recess, and weld material disposed within the recess to substantially fill the recess to a level at least flush with the surface of the rim adjacent the recess. The crimp is preferably formed so as to provide a recess which opens onto the outer surface of the rim, with the weld material having a depth sufficient to fill the recess flush with the outer surface of the rim adjacent the recess formed by the crimp.
The invention further contemplates a method of constructing a wheel, substantially in accordance with the foregoing summary. In a preferred mode of carrying out the method, the recess is formed by circumferentially crimping the material of the rim. The mounting structure, e.g. the mounting tabs as summarized above, are then connected to the inner surface of the rim such as by welding. Thereafter, the recess formed by the circumferential crimp is filled with sufficient weld material to substantially fill the recess.